function images = loadMNISTImages(filename)
%load MNIST Images returns a 28x28x[number of MNIST images] matrix containing
% 原链接：https://blog.csdn.net/tracer9/article/details/51253604
%the raw MNIST images
  
fp = fopen(filename, 'rb');
assert(fp ~= -1, ['Could not open ', filename, '']);
  
magic = fread(fp, 1, 'int32', 0, 'ieee-be');
assert(magic == 2051, ['Bad magic number in ', filename, '']);
  
numImages = fread(fp, 1, 'int32', 0, 'ieee-be');
numRows = fread(fp, 1, 'int32', 0, 'ieee-be');
numCols = fread(fp, 1, 'int32', 0, 'ieee-be');
  
images = fread(fp, inf, 'unsigned char');
images = reshape(images, numCols, numRows, numImages);
images = permute(images,[2 1 3]);
  
fclose(fp);
  
% Reshape to #pixels x #examples
images = reshape(images, size(images, 1) * size(images, 2), size(images, 3));
% Convert to double and rescale to [0,1]
images = double(images) / 255;